1. Field of the Invention
The invention relates to tires of a motor vehicle. More specifically, the invention relates to testing stress levels along a periphery of a vehicular tire.
2. Description of the Related Art
Tires for a motor vehicle serve an essential part of the safety of the motor vehicle. In particular, the tires are responsible for ensuring the motor vehicle handles properly. Not only do the tires have an integral part in the proper handling, i.e., proper acceleration, deceleration and cornering, they also affect the ride and fuel consumption of the motor vehicle. Therefore, the tire provides the operator of a motor vehicle with a comfortable and fuel efficient motor vehicle.
Testing of the tire is important when determining the various properties of the tire. A tire undergoes a deformation during each rotation. Any abnormal deformation of the tire causes excessive stresses to occur and may lead to premature failure. The higher stresses and abnormal deformation lead to higher thermal generation. The key design characteristics for preventing the abnormal deformations are that of the carcass line and the mold contour. The carcass line is defined by the carcass, an element of the tire. The carcass extends between and is connected to the tire beads. The carcass extends through a tread portion of the tire substantially close to the inner surface of the tire. The mold contour includes the outer surface defined by the two sidewalls and the tread of the tire.
These two design characteristics are important in minimizing the abnormal deformations and, thus, high stresses and excess thermal energy generated by the tire under deformation. It would be beneficial to have a relatively simple test that can be utilized to evaluate the stresses of a tire when it is deformed. Such a test would allow a designer of a tire the ability to modify a mold contour with respect to a carcass extending through a carcass line to minimize stresses and enhance the performance and reliability of the tire.
U.S. Pat. No. 2,251,803, issued to Pummill on Aug. 5, 1941, discloses a tire tester. The tire tester tests a tire casing for structural defects while in place on a vehicle wheel mounted to a vehicle. The testing device includes a roller which is recessed within a pit for placement of a vehicle tire thereon. The roller is connected to a motor for variably controlling the velocity of the tire. The testing device further includes contact mechanisms, such as bellows, interconnected to a pressure gauge by a tube. The bellows are placed on either side of the tire in contact with the tread of the tire. When the testing device is activated, the tire begins rotating. The tire tester is a dynamic testing system. The bellows follow the contours of the tire and indicate any structural defects in the tire up on the pressure gauge.
The above-cited reference discloses a testing apparatus that relates only to bias tires. Radial tires were yet to be invented when the patent application was filed, 1937. The contour of the bias tire carcass and carcass line the column bigger when its inflation pressure becomes higher. Conversely, a radial tire, properly designed, does not sustain any significant change when inflated at various pressures. The invariance of the length of the radial carcass line in the presence of very stiff steel belts under the tread justify the fact that a simple one-inch radial tire section can adequately represent the tire contour in-service. This is not the case for a bias tire. Therefore, the testing apparatus of the Pummill ""803 reference is required for a bias tire because the full casing must be inflated under pressure before it can be properly evaluated.
A testing assembly calculates stress levels along a cross section of a pneumatic tire having tire beads, sidewalls, and the tread. The testing assembly includes a base defining a base surface. A plurality of mounts are slidably secured to the base surface. Each of the tire beads are secured to each of the plurality of mounts. The tire beads are mounted thereto in a manner to simulate the mounting of a tire to a rim of a wheel. The testing assembly also includes a platform that extends parallel to the base surface. The platform is engagable with the tread of the tire and is movable with respect to the base. The movement of the platform simulates the tire under a load by deforming the tire.